Ignore the loader's PT_GNU_STACK when calculating the stack size, and onlyconsider the executable's PT_GNU_STACK, assuming the executable has one.

Currently the behaviour is to take the largest stack size and use that, butthat means you can't reduce the stack size in the executable. The loader'sstack size should probably only be used when executing the loader directly.

WARNING: This patch is slightly dangerous - it may render a system inoperableif the loader's stack size is larger than that of important executables, andthe system relies unknowingly on this increasing the size of the stack.